import com.mysql.jdbc.jdbc2.optional.MysqlDataSource;

import javax.sql.DataSource;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

// 通过这个类封装 DataSource.
public class DBUtil {
    private DBUtil() { }
    private static volatile DataSource dataSource = null;

    private static DataSource getDataSource() {
        if (dataSource == null) {
            synchronized (DBUtil.class) {
                if (dataSource == null) {
                    dataSource = new MysqlDataSource();
                    ((MysqlDataSource) dataSource).setUrl(
                            "jdbc:mysql://127.0.0.1:3306/blog_system?characterEncoding=utf8&useSSL=false");
                    ((MysqlDataSource) dataSource).setUser("root");
                    ((MysqlDataSource) dataSource).setPassword("1111");
                }
            }
        }
        return dataSource;
    }

    // 封装建立连接操作.
    public static Connection getConnection() throws SQLException {
        return getDataSource().getConnection();
    }
    // 关闭连接 释放资源.
    public static void close(Connection connection, PreparedStatement statement, ResultSet resultSet) {
        // 创建顺序是: connection -> statement -> resultSet
        // 释放顺序是: resultSet -> connection -> statement

        if (resultSet != null) {
            try {
                resultSet.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }

        if (statement != null) {
            try {
                statement.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }

        if (connection != null) {
            try {
                connection.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }

    }
}
